Field
Communication systems, such as an evolved packet system, may benefit from various interworking functions. In particular, certain communication systems in which machine type communication devices are deployed may benefit from machine type communication interworking functions.
Description of the Related Art
The evolved packet system (EPS), the successor of general packet radio system (GPRS), provides radio interfaces and packet core network functions for broadband wireless data access. EPS core network functions may comprise the mobility management entity (MME), the packet data network gateway (PDN-GW) and the Serving Gateway (S-GW). An example of an evolved packet core architecture is illustrated in FIG. 1 and is described by third generation partnership project (3GPP) technical specification (TS) 23.401, which is incorporated herein by reference in its entirety. A common packet domain core network can be used for different radio access networks (RANs) types, like for example the global system for mobile communication (GSM) enhanced data rates for GSM evolution (EDGE) radio access network (GERAN) and the universal terrestrial radio access network (UTRAN).
For machine-type-communication (MTC) a functional entity called MTC interworking function (MTC-IWF) and several new interfaces, comprising S6m, Tsp, Tsms, T5a/b/c and T4, have been introduced to the 3GPP architecture. FIG. 2 illustrates machine-type-communication additions to the 3GPP architecture, as well as the various interfaces identified. The MTC-IWF and the new interfaces in 3GPP Release 11 (Rel 11) can, for example, enable triggering of devices with or without a mobile subscriber integrated services digital network number (MSISDN) from an internal or external MTC server. The triggering of the devices may be, for example, in order to establish a packet data network (PDN) connection and/or packet data protocol (PDP) context. A 3GPP architecture for machine-type communication is discussed in 3GPP TS 23.682, which incorporated herein by reference in its entirety.
Conventionally, a system can locate an interworking function in a home network (as shown in FIG. 2) and perform T5 based triggering as shown in the call flow in FIG. 3. In roaming scenarios this results in introduction of charging functionality in the MME to allow for inter-operator charging, possible security threats to the serving network nodes in the visited network and exposes the serving network topology to the outside world.
As shown in FIG. 3, at 1 a submit request can be received at a serving GPRS support node (SGSN)/MME/MSC from a MTC-IWF located in the home network. Charging data record (CDR) generation can occur in the SGSN/MME/MSC in the visited network. Then, at 2, a transfer trigger can arise. Therefore, at 3, the MTC-IWF can receive a delivery report from the SGSN/MME/MSC. After that, at 4, the MTC-IWF can register for UE reachability notification by contacting the home subscriber server (HSS) to provide store and forward functionality if there is a failure in trigger delivery.
“Device reachability” can be an important feature of 3GPP related to device triggering and specifically T5 based device triggering. MTC interworking function in the current architecture, however, is present in the home network, as shown in FIG. 2. Thus, there is a need to support charging functionality in the serving node (for example MME) to address inter-operator charging in case of roaming scenarios for T5 based triggering and other T5based features like small data transmission and monitoring to work.
Furthermore, because the trigger message and other downlink messages are sent directly from the MTC-IWF to the serving node (for example MME), a fake IWF could bombard the serving node (for example the MME) in the serving network with fake trigger messages. If the trigger message is based on mobile terminated short message service (MT-SMS), then the fake triggers can also be initiated by hackers using, for example, Internet, malicious applications, or the like. Moreover, the internal network topology has to be exposed for the MTC-IWF to deliver the trigger message directly to the correct serving nodes.